Diego Costa's form has dipped since Chelsea rejected a January approach from TianjinCredit: REUTERS

Tianjin owner Shu Yuhui said: “The only thing I can reveal right now is that we have agreed terms with two or three stars. The players have no problem with the deals and their clubs are also willing to let them leave. The only issue that remains unresolved is reaching agreements with their respective clubs over the transfer fees.”

Chelsea are unlikely to reject a bid of £76m for Costa, who turns 29 in October and will have two years remaining on his contract at the end of the season.

Asked specifically about Tianjin’s interest in Costa, Edinson Cavani, who has signed a new contract at Paris Saint-Germain, Radamel Falcao, Pierre-Emerick Aubameyang and Nikola Kalinic, Shu added: “It's safe to say we did make contact with all of those players, some of whom are still in talks with us.

“The player we buy should satisfy two requirements. First, he is suitable to the style of football we play and second, he has the right attitude. However, if some clubs are intent on taking advantage of us, we won't allow ourselves to get ripped off. We won't lose our mind.”

The only potential stumbling block to Tianjin’s bid for Costa appears to be if a big European club, such as Paris Saint-Germain or Inter Milan, make a lucrative offer.

Costa has told friends that he would seriously consider a move to Paris, but the French club have been linked heavily with Borussia Dortmund striker Aubameyang.

Despite the fact he has helped fire Chelsea towards a Premier League and FA Cup double with 20 goals in all competitions, Costa’s form has dipped dramatically during the second half of the season.

Costa rowed with head coach Antonio Conte in the aftermath of Tianjin’s failed January offer before a truce was struck to protect Chelsea’s bid for silverware.

But Costa has scored just six goals since the fall-out and has admitted on several occasions that he asked to leave Chelsea last summer and remains unhappy with the English weather.

He was left out of the starting line-up for the FA Cup semi-final victory over Tottenham Hotspur at Wembley, but returned to score twice against Southampton.

Conte has continued publicly to back Costa without giving any guarantees over his future past this season and the club appreciate the part he has played in Chelsea’s bid to complete the double.

But there is a growing sense of weariness regarding Costa’s inability to settle and a feeling that a new issue will emerge each season if he is not allowed to leave.

Chelsea have also considered the fact they would have to offer Costa a new contract to stay past this campaign.

Should Costa complete a move to Tianjin, then Chelsea will have collected £161m in transfer fees from Chinese clubs in 18 months for the Spain international, Oscar and Ramires.

There is also Chinese interest in 28-year-old Willian, who has become frustrated at spending so much time on the Chelsea substitutes’ bench behind Pedro this season.

Other than chasing Lukaku, Chelsea hope to sign central defender Virgil van Dijk from Southampton. They are interested in Monaco midfielder Tiemoué Bakayoko and want at least one new wing-back as part of a summer spend that could hit £200m.

Chelsea are also determined to hang on to both Eden Hazard and Thibaut Courtois, who have been linked with Real Madrid, and plan to offer the Belgian pair new contracts at the end of the season.